U.S. patent application number 12/289711 was filed with the patent office on 2010-01-21 for motor, compressor and air conditioning system having the same.
This patent application is currently assigned to LG ELECTRONICS INC.. Invention is credited to Seung-Hyoung Ha, Geun-Hyoung Lee, Kang-Wook Lee, Hyuk Nam.
Application Number | 20100011806 12/289711 |
Document ID | / |
Family ID | 40564911 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100011806 |
Kind Code |
A1 |
Nam; Hyuk ; et al. |
January 21, 2010 |
Motor, compressor and air conditioning system having the same
Abstract
The present invention provides a motor, comprising: a stator
including a coil wiring portion to which power is supplied; a
rotor, which includes conductive bars, flux barriers, and permanent
magnets, and rotates through an interactive electromagnetic force
between the conductive bars, flux barriers, and permanent magnets
and the coil wiring portion of the stator; an integrated capacitor,
which is electrically connected to the coil wiring portion and
includes two capacitors connected to each other in parallel, an
electrical switch serially connected to one of the two capacitors,
and a casing on which the two capacitors and the electrical switch
are securely mounted.
Inventors: |
Nam; Hyuk; (Masan-si,
KR) ; Lee; Kang-Wook; (Changwon-si, KR) ; Ha;
Seung-Hyoung; (Changwon-si, KR) ; Lee;
Geun-Hyoung; (Suyeong-gu, KR) |
Correspondence
Address: |
MCKENNA LONG & ALDRIDGE LLP
1900 K STREET, NW
WASHINGTON
DC
20006
US
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
40564911 |
Appl. No.: |
12/289711 |
Filed: |
October 31, 2008 |
Current U.S.
Class: |
62/510 ;
310/156.83; 318/795; 418/136; 418/209 |
Current CPC
Class: |
H02K 21/46 20130101;
F04C 2270/56 20130101; H02K 1/246 20130101; H02K 17/165 20130101;
F04C 18/3564 20130101; F04C 28/06 20130101; F04C 29/0085 20130101;
F04C 23/008 20130101; F04C 23/001 20130101; F04C 2240/803
20130101 |
Class at
Publication: |
62/510 ;
310/156.83; 318/795; 418/136; 418/209 |
International
Class: |
F25B 49/02 20060101
F25B049/02; F25B 1/04 20060101 F25B001/04; H02K 21/46 20060101
H02K021/46; H02P 1/44 20060101 H02P001/44; F25B 1/10 20060101
F25B001/10; F04C 18/00 20060101 F04C018/00; F04C 28/02 20060101
F04C028/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2008 |
KR |
10-2008-0069307 |
Claims
1. A compressor provided with a casing defining a hermetic space, a
compression mechanism for compressing a refrigerant, and a motor
for driving the compression mechanism, the motor comprising: a
stator including a coil wiring portion to which common power is
supplied; a rotor which includes a rotor core, conductive bars,
flux barriers, and permanent magnets, rotates by interactive
electromagnetic forces like an induction torque generated between
the conductive bars and the coil wiring portion, a reluctance
torque generated between the flux barriers and the coil wiring
portion, and a magnetic torque generated between the permanent
magnets and the coil wiring, and has a load torque of a startup
operation different from a load torque during a normal operation;
and an integrated capacitor unit which is electrically connected to
the coil wiring portion and includes a plurality of capacitors with
a variable capacity in accordance with a load torque placed on the
rotor.
2. The compressor of claim 1, wherein the capacitor unit includes
two capacitors connected to each other in parallel in a casing to
configure a shell of the capacitor unit, and one of the two
capacitors is connected to an electrical switch to vary the
capacitance of capacitors.
3. The compressor of claim 2, wherein the electrical switch is a
PTC device.
4. The compressor of claim 2, wherein a sum of capacities of
capacitors that are not connected serially to the electrical switch
has a rated capacity suitable for a synchronous speed
operation.
5. The compressor of claim 1, wherein the compression mechanism is
configured with at least one rotary compressor unit which includes
a cylinder functioning as a compression chamber, a rolling piston
rotating inside the cylinder under a torque having been transferred
from a motor through a shaft, and a vane partitioning off the
interior space of the cylinder into a compression chamber and a
suction chamber.
6. The compressor of claim 5, wherein the compression mechanism is
a capacity modulation compressor which includes a plurality of
rotary compressor units to modulate a total compressing capacity of
the compressor units through the control of an operation of each of
the rotary compressor units.
7. The compressor of claim 5, wherein the compression mechanism is
a capacity modulation compressor including a plurality of rotary
compressor units, a suction pipe passing through a casing to let a
working fluid intaken by a cylinder, and a suction valve installed
on the suction pipe to open or close the suction pipe, such that a
total compressing capacity of the compressor units varies depending
on whether the suction valve is open or closed.
8. The compressor of claim 5, wherein the compression mechanism is
a capacity modulation compressor unit comprising a plurality of
rotary compressor units, and at least one of the rotary compressor
units includes a vane slit in which a vane is inserted, a back
pressure space communicating with the vane slit from an
circumference side of the vane slit, and a vane control unit for
supplying a suction pressure or a discharge pressure to a rear face
of the vane to support the vane and for supplying a discharge
pressure to a lateral face of the vane at the same time, such that
a difference between the pressure applied to the rear face of the
vane and the pressure applied to the lateral face of the vane makes
the vane bound or released, thereby making the vane contacted with
or separated from a rolling piston, and wherein the compression
mechanism is a capacity modulation compressor capable of modulating
a total compressing capacity of the compressor units by controlling
the operation of at least one of the cylinder rotary compressor
units.
9. The compressor of claim 8, wherein the vane control unit
includes a back pressure connection pipe via which a working fluid
is introduced into the back pressure space; a low pressure
connection pipe connected to the back pressure connection pipe, via
which a low pressure non-compressed working fluid flows; a high
pressure connection pipe connected to the back pressure connection
pipe, via which a high pressure compressed working fluid flows; a
valve for opening/closing the low pressure connection pipe; and a
valve for opening/closing the high pressure connection pipe.
10. The compressor of claim 8, wherein the vane control unit
includes a back pressure connection pipe via which a working fluid
is introduced into the back pressure space; a low pressure
connection pipe connected to the back pressure connection pipe, via
which a low pressure non-compressed working fluid flows; a high
pressure connection pipe connected to the back pressure connection
pipe, via which a high pressure compressed working fluid flows; a
switch valve for regulating the flow of a working fluid being
introduced into the back pressure space through the back pressure
connection pipe.
11. The compressor of claim 10, wherein the switch valve is a
three-way valve for alternately connecting the low pressure
connection pipe and the high pressure connection pipe to the back
pressure connection pipe.
12. An air conditioning system provided with an indoor unit
composed of a compressor including a motor and a compression
mechanism, a condenser, and a heat exchanger, wherein the motor
includes a rotor core, conductive bars, flux barriers, and
permanent magnets, rotates by interactive electromagnetic forces
like an induction torque generated between the conductive bars and
the coil wiring portion, a reluctance torque generated between the
flux barriers and the coil wiring portion, and a magnetic torque
generated between the permanent magnets and the coil wiring, and
has a load torque of a startup operation different from a load
torque during a normal operation; and an integrated capacitor unit
which is electrically connected to the coil wiring portion and
includes a plurality of capacitors with a variable capacity in
accordance with a load torque placed on the rotor.
13. The system of claim 12, wherein a sum of capacitance of
capacitors included in the capacitor unit is sufficiently high for
the motor to produce a larger starting torque than a load torque
during a startup.
14. The system of claim 12, wherein the capacitor unit includes two
capacitors that are connected to each other in parallel and are
positioned inside a casing to configure a shell of the capacitor
unit, and one of the two capacitors is connected to an electrical
switch to vary the capacitance of capacitors.
15. The system of claim 14, wherein the electrical switch is a PTC
device.
16. The system of claim 14, wherein a sum of capacities of
capacitors that are not connected serially to the electrical switch
has a rated capacity suitable for a synchronous speed
operation.
17. The system of claim 14, wherein the electrical switch is turned
off when the motor operates at a synchronous speed.
18. The system of claim 12, wherein the compression mechanism is
configured with at least one rotary compressor unit which includes
a cylinder functioning as a compression chamber, a rolling piston
rollting inside the cylinder under a torque transferred from a
motor through a shaft, and a vane partitioning off the interior
space of the cylinder into a compression chamber and a suction
chamber.
19. The system of claim 18, wherein the compression mechanism is a
capacity modulation compressor including a plurality of rotary
compressor units, a suction pipe passing through a casing to let a
working fluid intaken by a cylinder, and a suction valve installed
on the suction pipe to open or close the suction pipe, such that a
total compressing capacity of the compressor units varies depending
on whether the suction valve is open or closed.
20. The system of claim 18, wherein the compression mechanism is a
capacity modulation compressor comprising a plurality of rotary
compressor units, and at least one of the rotary compressor units
includes a vane slit in which a vane is inserted, a back pressure
space communicating with the vane slit from an circumference side
of the vane slit, and a vane control unit for supplying a suction
pressure or a discharge pressure to a rear face of the vane to
support the vane and for supplying a discharge pressure to a
lateral face of the vane at the same time, such that a difference
between the pressure applied to the rear face of the vane and the
pressure applied to the lateral face of the vane makes the vane
bound or released, thereby making the vane contacted with or
separated from a rolling piston, and wherein the compression
mechanism is a capacity modulation compressor capable of modulating
a total compressing capacity of the compressor units by controlling
the operation of at least one of the rotary compressor units.
21. A motor, comprising: a stator including a coil wiring portion
to which common power is supplied; a rotor which includes a rotor
core, conductive bars, flux barriers, and permanent magnets,
rotates by interactive electromagnetic forces like an induction
torque generated between the conductive bars and the coil wiring
portion, a reluctance torque generated between the flux barriers
and the coil wiring portion, and a magnetic torque generated
between the permanent magnets and the coil wiring, and has a load
torque of a startup operation different from a load torque during a
normal operation; and an integrated capacitor unit which is
electrically connected to the coil wiring portion and includes a
plurality of capacitors with a variable capacity in accordance with
a load torque placed on the rotor.
22. The motor of claim 21, wherein a sum of capacitance of
capacitors included in the capacitor unit is sufficiently high for
the motor to produce a larger starting torque than a load torque
during a startup.
23. The motor of claim 21, wherein the capacitor unit includes two
capacitors, inside a casing to configure a shell of the capacitor
unit, connected to each other in parallel, and one of the two
capacitors is connected to an electrical switch to vary the
capacitance of capacitors.
24. The motor of claim 23, wherein the electrical switch is a PTC
device.
25. The motor of claim 23, wherein a sum of capacities of
capacitors that are not connected serially to the electrical switch
has a rated capacity suitable for a synchronous speed
operation.
26. The motor of claim 23, wherein the electrical switch is turned
off when the motor operates at a synchronous speed.
27. The motor of claim 23, wherein a discharge resistor is formed
on the capacitor connected serially to the electrical switch.
28. The motor of claim 21, wherein the coil wiring portion is
composed of a main wiring connected to a common power supply and an
auxiliary wiring connected to the main wiring in parallel, and the
capacitor unit is connected serially to the auxiliary wiring.
29. The motor of claim 21, wherein the rotor is structured in a
manner that a plurality of conductive bars are arranged in a
circumference direction on the inner side of the rotor core.
30. The motor of claim 29, wherein the rotor has a q-axis along
which the flux flow is impeded due to the presence of flux barriers
and a d-axis along which the flux flow is not impeded.
31. The motor of claim 30, wherein the conductive bars positioned
close to the q-axis is larger than the conductive bars positioned
close to the d-axis.
32. The motor of claim 31, wherein the flux barriers are arranged
to form an even number not smaller than two of poles.
33. The motor of claim 31, wherein the flux barriers impede the
flux flow in a radial direction of the rotor.
34. The motor of claim 21, wherein the rotor is expressed in a
q-axis along which the flux flow is resisted due to the presence of
flux barriers and in a d-axis along which the flux flow is not
impeded.
35. The motor of claim 34, wherein the q-axis and the d-axis are
orthogonal to each other at the center of the rotor.
36. The motor of claim 34, wherein the flux barriers are formed in
plural pairs symmetric with respect to the q-axis.
37. The motor of claim 34, wherein the flux barriers are inclined
at a predetermined angle with respect to the d-axis.
38. The motor of claim 21, wherein the permanent magnets are
inserted into the flux barriers.
39. The motor of claim 21, wherein the rotor further comprises end
rings provided to the upper and lower portions of the rotor core,
which do not interfere with the permanent magnets but form a short
circuit with the plural conductive bars.
40. The motor of claim 39, wherein the end ring provided to the
upper portion of the rotor core has a radial width shorter in the
q-axis direction than in the d-axis direction.
Description
[0001] This application claims the benefit of Korean Patent
Application No. 10-2008-0069307 filed on Jul. 16, 2008, which is
hereby incorporated by reference in its entirety as if fully set
forth herein.
FIELD OF THE INVENTION
[0002] The present invention relates to a motor, more specifically,
to a motor having high efficiency by minimizing power loss. The
motor can produce a higher starting torque, and rotate at a preset
synchronous speed in normal operation mode.
BACKGROUND OF THE INVENTION
[0003] In general, a single phase induction motor includes a stator
wound around with a main coil and a sub-coil which are physically
spaced 900 apart from each other, and a supply power is applied
directly to the main coil, while indirectly (i.e., via a capacitor
and a switch) to the sub-coil. This is because the single phase
induction motor would not start even if a voltage is applied to the
main coil. Therefore, a starting device such as the sub-coil is
needed to create a rotor system at the stator, thereby starting or
actuating the rotor.
[0004] There are many types of starting devices, for example, split
phase start type, shaded coil start type, capacitor start type,
repulsion start type, etc.
[0005] An capacitor start-type single phase induction motor is
described as an example of a single phase induction motor, with
reference to FIG. 1 and FIG. 2.
[0006] FIG. 1 illustrates a stator 10 and a rotor 20 in a
conventional single phase induction motor, and FIG. 2 illustrates a
simple circuit having a rotor coil and a stator coil.
[0007] When a main coil 12 is the only coil wound around the stator
10, only an alternating magnetic field is produced by the stator 10
and thus the rotor 20 does not start. However, when a sub-coil 14
is also wound around the stator to produce a rotating magnetic
field whereby the rotor starts running or rotating in a certain
direction. That is to say, the rotating magnetic field generates a
starting torque.
[0008] Meanwhile, a capacitor 15 causes a phase delay of current
being applied to the sub-coil 14 to generate a starting torque
through the interaction with the main coil 12. Once started, if
there is not going to be any change in a load, the rotor keeps
rotating even if the sub-coil is not fed with power. Therefore,
once the rotor started and keeps running at certain RPM or higher,
it is all right to stop the power supply to the sub-coil. However,
if the load is variable, a starting torque is needed. In this case,
the sub-coil must always be provided with power through the
capacitor.
[0009] On the contrary, a three-phase induction motor where a
rotation system is easily created even by winding only the main
coil around a stator, there is no need to wind the aforementioned
sub-coil around the stator. In other words, a separate starting
device is not necessary for the three-phase induction motor.
[0010] However, the single phase induction motor offers a
competitive advantage over others in terms of price in that it does
not require an inverter drive component of a BLDC (brushless DC)
motor or a reluctance motor and can start up with the help of a
common single phase power source.
[0011] Referring to FIG. 1 and FIG. 2, the detail description of
the general single phase induction motor will be followed.
[0012] The stator 10 has a hollow interior space, an inner
periphery of which is provided with a plurality of teeth 11
arranged at a predetermined angle interval, each being protruded
inwardly in a radius direction and each being wound with the main
coil 12 to have N-polarity or S-polarity at the application of a
primary current.
[0013] An insulator (not shown) is provided between each of the
teeth 11 and the main coil 12 to insulate between the tooth and the
main boil and to facilitate the winding of the main coil.
[0014] The stator 10 also includes the sub-coil 14 that is wound
physically spaced apart from the main coil 12 at a predetermined
angle to produce a rotating magnetic field when current is applied
thereto. Of course, the sub-coil is wound around the teeth 11 via
the insulator, and the main coil 12 and the sub-coil 14 together
are called a stator coil or simply a coil.
[0015] The coils 12 and 14 are connected to a single phase power
source, in parallel to each other. Moreover, the sub-coil is
serially connected to the capacitor 15. Although not shown, the
capacitor may be connected selectively to the power source through
a switch.
[0016] Generally, a squirrel cage rotor is used most in the field,
so the rotor 20 shown in FIGS. 1 and 2 represent the squirrel cage
rotor.
[0017] The rotor 20 is formed by stacking a plurality of
identically shaped steel sheets, each steel sheet having a
plurality of slots 21 formed at a predetermined angle interval
along the outer circumference at a predetermined radial position
from the core. In addition, the rotor 20 includes conductive bars
22 inserted into the slots 21 of the rotor core, and the conductive
bar is usually made out of copper or aluminum.
[0018] In order to cause an electrical short through the conductive
bars, both ends of the squirrel cage rotor are connected by an end
ring (not shown in FIGS. 1 and 2, referred to FIGS. 11 and 12
later), and the end ring is typically formed by an aluminum die
casting process. That is, the conductive bar 22 and the end ring
are integrated through aluminum die casting, and the end ring is
formed at the upper and lower portions of the rotor core,
respectively. Meanwhile, an axial bore 24 is formed in the core of
the rotor 20, and a shaft (not shown) transferring torque of the
rotor to other components is press fitted into the axial bore such
that the rotor and the shaft can rotate in one unit.
[0019] According to how the single phase induction motor with the
above configuration works, when power is applied to the coil, an
induced current is produced in the conductive bars 22, through
which an induction torque is generated to rotate the motor. In this
case, however, a loss occurs in a the conductive bars 22, the loss
is so called a conductive bar loss. Because of the conductive bar
loss, there is a limitation in enhancing the efficiency of a motor
with a fixed size. Therefore, single phase induction motors were
not suitable, sometimes useless, for high-efficiency work.
[0020] Besides, the rotor 20 gets hot because of the conductive bar
loss, and such a temperature change of the rotor in turn made the
loss even higher. In other words, the conductive bar loss gets
worse as the temperature of the rotor increases. This remained as
another limitation in improving the efficiency of a motor at high
temperature.
[0021] In the meantime, it is known that the single phase induction
motor, by its nature, should always run slower than a preset
synchronous speed, to be able to produce an induced torque. This is
because, theoretically, the amount of torque of the single phase
induction motor stays zero at the synchronous speed, and it tends
to increase at low RPMs.
[0022] In short, a problem arises in the single phase induction
motor in relation to the control of the motor in response to a
change in the motor load since the speed of the motor shaft, i.e.,
the motor speed, varies with the load on the motor, i.e., the load
on the motor shaft.
DISCLOSURE
Technical Problem
[0023] An object of the present invention is to provide a motor
having high-efficiency for improving the efficiency of a
compressor.
[0024] Another object of the present invention is to provide a
motor having high efficiency of startup and normal operations,
without an inverter driver.
[0025] Still another object of the present invention is to provide
a motor capable of making an active transition from a startup mode
to a normal operation mode, in the absence of the control offered
by a separate controller.
Technical Solution
[0026] According to the present invention, there is provided a
compressor provided with a casing defining a hermetic space, a
compression mechanism for compressing a refrigerant, and a motor
for driving the compression mechanism, the motor comprising: a
stator including a coil wiring portion to which common power is
supplied; a rotor which includes a rotor core, conductive bars,
flux barriers, and permanent magnets, rotates by interactive
electromagnetic forces like an induction torque generated between
the conductive bars and the coil wiring portion, a reluctance
torque generated between the flux barriers and the coil wiring
portion, and a magnetic torque generated between the permanent
magnets and the coil wiring, and has a load torque of a startup
operation different from a load torque during a normal operation;
and an integrated capacitor unit which is electrically connected to
the coil wiring portion and includes a plurality of capacitors with
a variable capacity in accordance with a load torque placed on the
rotor.
[0027] According to another aspect of the present invention, the
capacitor unit includes two capacitors connected to each other in
parallel in a casing to configure a shell of the capacitor unit,
and one of the two capacitors is connected to an electrical switch
to vary the capacitance of capacitors.
[0028] According to another aspect of the present invention, the
electrical switch is a PTC device.
[0029] According to another aspect of the present invention, a sum
of capacities of capacitors that are not connected serially to the
electrical switch has a rated capacity suitable for a synchronous
speed operation of the motor.
[0030] According to another aspect of the present invention, the
compression mechanism includes at least one rotary compressor unit
which includes a cylinder functioning as a compression chamber, a
rolling piston rolling inside the cylinder by a torque transferred
from a motor through a shaft, and a vane partitioning off the
interior space of the cylinder into a compression chamber and a
suction chamber.
[0031] According to another aspect of the present invention, the
compression mechanism is a capacity modulation compressor unit
which includes a plurality of rotary compressor units to modulate a
total compressing capacity of the compressor units through the
control of an operation of each of the rotary compressor units.
[0032] According to another aspect of the present invention, the
compression mechanism is a capacity modulation compressor unit
including a plurality of rotary compressor units, a suction pipe
passing through a casing to let a working fluid intaken by a
cylinder, and a suction valve installed on the suction pipe to open
or close the suction pipe, such that a total compressing capacity
of the compressor units varies depending on whether the suction
valve is open or closed.
[0033] According to another aspect of the present invention, the
compression mechanism is a capacity modulation compressor unit
comprising a plurality of rotary compressor units, and at least one
of the rotary compressor units includes a vane slit in which a vane
is inserted, a back pressure space communicating with the vane slit
from an circumference side of the vane slit, and a vane control
unit for supplying a suction pressure or a discharge pressure to a
rear face of the vane to support the vane and for supplying a
discharge pressure to a lateral face of the vane at the same time,
such that a difference between the pressure applied to the rear
face of the vane and the pressure applied to the lateral face of
the vane makes the vane bound or released, thereby making the vane
contacted with or separated from a rolling piston, and wherein the
compression mechanism is a capacity modulation compressor capable
of modulating a total compressing capacity of the compressor units
by controlling the operation of at least one of the cylinder rotary
compressor units.
[0034] According to another aspect of the present invention, the
vane control unit includes a back pressure connection pipe via
which a working fluid is introduced into the back pressure space, a
low pressure connection pipe connected to the back pressure
connection pipe, via which a low pressure non-compressed working
fluid flows, a high pressure connection pipe connected to the back
pressure connection pipe, via which a high pressure compressed
working fluid flows, a valve for opening/closing the low pressure
connection pipe and a valve for opening/closing the high pressure
connection pipe.
[0035] According to another aspect of the present invention, the
vane control unit includes a back pressure connection pipe via
which a working fluid is introduced into the back pressure space, a
low pressure connection pipe connected to the back pressure
connection pipe, via which a low pressure non-compressed working
fluid flows, a high pressure connection pipe connected to the back
pressure connection pipe, via which a high pressure compressed
working fluid flows and a switch valve for regulating the flow of a
working fluid being introduced into the back pressure space through
the back pressure connection pipe.
[0036] According to another aspect of the present invention, the
switch valve is a three-way valve for alternately connecting the
low pressure connection pipe and the high pressure connection pipe
to the back pressure connection pipe.
[0037] Furthermore the present invention provides an air
conditioning system provided with a compressor including a motor
and a compression mechanism, and an indoor unit having condenser
and a heat exchanger, wherein the motor includes a rotor core,
conductive bars, flux barriers, and permanent magnets, wherein, the
rotor core, conductive bars, flux barriers, and permanent magnets
configure, rotates by interactive electromagnetic forces like an
induction torque generated between the conductive bars and the coil
wiring portion, a reluctance torque generated between the flux
barriers and the coil wiring portion and a magnetic torque
generated between the permanent magnets and the coil wiring, and
has a load torque of a startup operation different from a load
torque during a normal operation; and an integrated capacitor unit
which is electrically connected to the coil wiring portion and
includes a plurality of capacitors with a variable capacity in
accordance with a load torque placed on the rotor.
[0038] According to another aspect of the present invention, a sum
of capacitance of capacitors included in the capacitor unit is
sufficiently high for the motor to produce a larger starting torque
than a load torque during a startup.
[0039] According to another aspect of the present invention, the
capacitor unit includes two capacitors that are connected to each
other in parallel and are positioned inside a casing to configure a
shell of the capacitor unit, and one of the two capacitors is
connected to an electrical switch to vary the capacitance of
capacitors.
[0040] According to another aspect of the present invention, the
electrical switch is a PTC device.
[0041] According to another aspect of the present invention, a sum
of capacities of capacitors that are not connected serially to the
electrical switch has a rated capacity suitable for a synchronous
speed operation.
[0042] According to another aspect of the present invention, the
electrical switch is turned off when the motor operates at a
synchronous speed.
[0043] According to another aspect of the present invention, the
compression mechanism comprises at least one rotary compressor unit
which includes a cylinder functioning as a compression chamber, a
rolling piston rolling inside the cylinder under a torque
transferred from a motor through a shaft, and a vane partitioning
off the interior space of the cylinder into a compression chamber
and a suction chamber.
[0044] According to another aspect of the present invention, the
compression mechanism is a capacity modulation compressor unit
including a plurality of rotary compressor units, a suction pipe
passing through a casing to let a working fluid intaken by a
cylinder, and a suction valve installed on the suction pipe to open
or close the suction pipe, such that a total compressing capacity
of the compressor units varies depending on whether the suction
valve is open or closed.
[0045] According to another aspect of the present invention, the
compression mechanism is a capacity modulation compressor
comprising a plurality of rotary compressor units, and at least one
of the rotary compressor units includes a vane slit in which a vane
is inserted, a back pressure space communicating with the vane slit
from an circumference side of the vane slit, and a vane control
unit for supplying a suction pressure or a discharge pressure to a
rear face of the vane to support the vane and for supplying a
discharge pressure to a lateral face of the vane at the same time,
such that a difference between the pressure applied to the rear
face of the vane and the pressure applied to the lateral face of
the vane makes the vane bound or released, thereby making the vane
contacted with or separated from a rolling piston, and wherein the
compression mechanism is a capacity modulation compressor capable
of modulating a total compressing capacity of the compressor units
by controlling the operation of at least one of the rotary
compressor units.
[0046] Furthermore the present invention provides a motor,
comprising: a stator including a coil wiring portion to which
common power is supplied; a rotor which includes a rotor core,
conductive bars, flux barriers, and permanent magnets, rotates by
interactive electromagnetic forces like an induction torque
generated between the conductive bars and the coil wiring portion,
a reluctance torque generated between the flux barriers and the
coil wiring portion, and a magnetic torque generated between the
permanent magnets and the coil wiring, and has a load torque of a
startup operation different from a load torque during a normal
operation; and an integrated capacitor unit which is electrically
connected to the coil wiring portion and includes a plurality of
capacitors with a variable capacity in accordance with a load
torque placed on the rotor.
[0047] According to another aspect of the present invention, a sum
of capacitance of capacitors included in the capacitor unit is
sufficiently high for the motor to produce a larger starting torque
than a load torque during a startup.
[0048] According to another aspect of the present invention, the
capacitor unit includes two capacitors that are connected to each
other in parallel inside a casing to configure a shell of the
capacitor unit, and one of the two capacitors is connected to an
electrical switch to vary the capacitance of capacitors.
[0049] According to another aspect of the present invention, the
electrical switch is a PTC device.
[0050] According to another aspect of the present invention, a sum
of capacities of capacitors that are not connected serially to the
electrical switch has a rated capacity suitable for a synchronous
speed operation.
[0051] According to another aspect of the present invention, the
electrical switch is turned off when the motor operates at a
synchronous speed.
[0052] According to another aspect of the present invention, a
discharge resistor is formed on the capacitor connected serially to
the electrical switch.
[0053] According to another aspect of the present invention, the
coil wiring portion comprises a main wiring connected to a common
power supply and an auxiliary wiring connected to the main wiring
in parallel, and the capacitor unit is connected serially to the
auxiliary wiring.
[0054] According to another aspect of the present invention, the
rotor is structured in a manner that a plurality of conductive bars
are arranged in a circumference direction on the inner side of the
rotor core.
[0055] According to another aspect of the present invention, the
rotor has a q-axis along which the flux flow is impeded due to the
presence of flux barriers and a d-axis along which the flux flow is
not resisted.
[0056] According to another aspect of the present invention, the
conductive bars positioned close to the q-axis is larger than the
conductive bars positioned close to the d-axis.
[0057] According to another aspect of the present invention, the
flux barriers are arranged to form an even number not smaller than
two of poles.
[0058] According to another aspect of the present invention, the
flux barriers impede the flux flow in a radial direction of the
rotor.
[0059] According to another aspect of the present invention, the
rotor is expressed in a q-axis along which the flux flow is
resisted due to the presence of flux barriers and in a d-axis along
which the flux flow is not impeded.
[0060] According to another aspect of the present invention, the
q-axis and the d-axis are orthogonal to each other at the center of
the rotor. According to another aspect of the present invention,
the flux barriers are formed in plural pairs symmetric with respect
to the q-axis.
[0061] According to another aspect of the present invention, the
flux barriers are inclined at a predetermined angle with respect to
the d-axis.
[0062] According to another aspect of the present invention, the
permanent magnets are inserted into the flux barriers.
[0063] According to another aspect of the present invention, the
rotor further comprises end rings provided to the upper and lower
portions of the rotor core, which do not interfere with the
permanent magnets but form a short circuit with the plural
conductive bars.
[0064] According to another aspect of the present invention, the
end ring provided to the upper portion of the rotor core has a
radial width shorter in the q-axis direction than in the d-axis
direction.
Advantageous Effects
[0065] The motor according to the present invention uses one
capacitor unit comprising two capacitors connected to each other in
parallel to overcome shortcomings of a line start permanent magnet
reluctance motor being assigned a larger load during a startup.
[0066] In addition, the motor in accordance with the present
invention includes an electrical switch connected serially to one
of those two capacitors. Therefore, when the startup operation, is
ended, the current flows to only one capacitor to thus prevent any
unnecessary increase in the capacity of the capacitors.
[0067] Unlike the structure of a conventional motor using two
parallel-connected capacitors, the motor according to the present
invention uses one single capacitor unit for more efficient drive
of the motor. As such, the motor according to the present invention
is much less confronted with space limitations during
installation.
[0068] Moreover, by the use of a PTC device as an electrical
switch, the motor of the present invention can actively cut off the
current flow to the start capacitor, even in the absence of an
ON/OFF command issued from the controller.
[0069] The other objectives and advantages of the invention will be
understood by the following description and will also be
appreciated by the embodiments of the invention more clearly.
Further, the objectives and advantages of the invention will
readily be seen that they can be realized by the means and its
combination specified in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0070] FIG. 1 is a cross-sectional view illustrating a rotor and a
stator of a conventional induction motor;
[0071] FIG. 2 is a conceptual view briefly illustrating a rotor and
a stator coil of a conventional induction motor;
[0072] FIG. 3 is a conceptual view briefly illustrating a rotor and
a stator coil circuit included in a motor in accordance with the
present invention;
[0073] FIG. 4 is an enlarged cross-sectional view of a portion
taken out of the rotor in FIG. 3;
[0074] FIG. 5a through FIG. 5c are cross-sectional views
illustrating different examples of an end of a flux barrier in FIG.
3;
[0075] FIG. 6 is an exploded perspective view of a rotor core for a
motor in accordance with the present invention;
[0076] FIG. 7 is a plan view of the uppermost layer of a rotor core
unit for a motor in accordance with one embodiment of the present
invention;
[0077] FIG. 8 is a plan view of the lowermost layer of a motor in
accordance with one embodiment of the present invention, or a plan
view of the uppermost layer of a rotor core unit in accordance with
another embodiment of the present invention;
[0078] FIG. 9 is a top plan view of a rotor for a motor in
accordance with one embodiment of the present invention;
[0079] FIG. 10 is a top plan view of a rotor for a motor in
accordance with one embodiment of the present invention, or a
bottom plan view of a rotor for a motor in accordance with another
embodiment of the present invention;
[0080] FIG. 11 is a perspective view illustrating only an upper end
ring of a motor in accordance with one embodiment of the present
invention;
[0081] FIG. 12 is a perspective view illustrating only a lower or
upper end ring for a motor in accordance with one embodiment of the
present invention;
[0082] FIG. 13 is a graph illustrating the relationship between
starting (or running) torque and capacitor for a motor in
accordance with one embodiment of the present invention;
[0083] FIG. 14 illustrates one example of a capacitor included in a
motor in accordance with the present invention;
[0084] FIG. 15 briefly illustrates a circuit diagram of a stator
coil and a capacitor included in a motor in accordance with the
present invention;
[0085] FIG. 16 graphically illustrates how a current flow in a
startup capacitor of the present invention changes with respect to
time;
[0086] FIG. 17 is a graph comparing torque a motor in accordance
with the present invention produces with torque a motor driven by a
conventional capacitor produces;
[0087] FIG. 18 illustrates a compression mechanism in accordance
with a first embodiment of the present invention;
[0088] FIG. 19 illustrates a compression mechanism in accordance
with a second embodiment of the present invention;
[0089] FIG. 20 is a graph comparing a starting torque produced by a
motor included in a compression mechanism in accordance with the
present invention with a starting torque produced by a conventional
induction motor;
[0090] FIG. 21 illustrates an air conditioning system in accordance
with one embodiment of the present invention;
[0091] FIG. 22 is a graph illustrating compressive load on an
outdoor unit including two fixed-capacity, fixed-speed compressors
in a prior art;
[0092] FIG. 23 is a graph illustrating compressive load on an
outdoor unit including one capacity modulation compressor in
accordance with one embodiment of the present invention and one
fixed-capacity, fixed-speed compressor;
[0093] FIG. 24 is a graph illustrating compressive load on an
outdoor unit including two capacity modulation compressors in
accordance with one embodiment of the present invention; and
[0094] FIG. 25 is a graph illustrating the load on an outdoor unit
including one capacity modulation compressor in accordance with one
embodiment of the present invention and one inverter
compressor.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0095] Hereinafter, preferred embodiments of a motor in accordance
with the present invention will be set forth in detail with
reference to the accompanying drawings FIGS. 3 through 15. In the
interest of brevity and convenience for explanation, an inner rotor
type motor provided with a rotor rotating inside a stator will be
explained, but a motor of the present invention is not limited to
the inner rotor type motor.
[0096] A motor in accordance with the present invention is
configured the same way as a regular induction motor in a prior
art, in which a rotor 120 starts running by an induction torque.
That is, the motor adopts the configuration of the induction motor,
as shown in FIG. 3, which includes a rotor 120 with slots 121 and
conductive bars 122, a stator coil 112 and 114 (hereinafter
referred to as a `coil`) for the rotation of the motor, and a
capacitor 115. Therefore, any descriptions below will not elaborate
on the same configuration between two motors.
[0097] Meanwhile, the motor in accordance with the present
invention includes a flux barrier 140 inside a rotor core 123 to
impede flux motion so that a reluctance torque may be generated.
Further, the motor in accordance with the present invention
includes permanent magnets 130 inside the rotor core 123 to produce
flux so that a magnetic torque may be generated.
[0098] Therefore, the motor in accordance of the present invention
starts to rotate taking on the property of induction motor, but in
normal operation mode it operates taking on the property of the
synchronous motor. In other words, once the motor has started, the
rotor 120 rotates at a preset synchronous speed by the reluctance
torque and the magnetic torque. Therefore, unlike any conventional
synchronous motors, the motor in accordance with the present
invention does not need a complicated, expensive configuration such
as an inverter driver, for a startup.
[0099] With reference to FIG. 3, the following will now explain in
detail about the basic principles for the reluctance torque and
magnetic torque generated by a motor in accordance with the present
invention.
[0100] The principle of reluctance torque generation will be
explained first.
[0101] As shown in FIG. 3, the flux barrier 140 is formed along
q-axis. Here, the flux barrier 140 is formed by removing a part of
the rotor core 123, the magnetic substance. That is, an air can be
filled in the flux barrier 140, and a nonmagnetic material, e.g.,
resin, may be filled.
[0102] When a current is fed to the coil and magnetic poles are
produced accordingly, magnetic flux is also formed in the rotor
130. However, a very high reluctance is generated due to the flux
barrier 140 along the q-axis where the flux barrier 140 is formed.
On the contrary, a very small reluctance is generated along d-axis
where the flux barrier 140 is not formed.
[0103] Therefore, the rotor 130 rotates in a direction to minimize
such a difference in reluctances in the q-axis and d-axis
directions, and this moment causing the rotor 130 to rotate is
called a reluctance torque. In effect, a larger difference in the
reluctances generates a greater reluctance torque.
[0104] Meanwhile, as shown in FIG. 3, the motor in accordance with
the present invention may further include permanent magnets 130.
Suppose that a current is fed to the coil and an N-magnetic pole is
formed. Then the permanent magnet may be magnetized to be the
S-magnetic pole. That is, at the position of the rotor 120 shown in
FIG. 3, the reluctance in the q-axis direction becomes much smaller
because of a offsetting between the flux produced by the stator and
the flux produced by the permanent magnets. In this way, the
difference in reluctances in the q- and d-axis directions can be
made even greater compared to a case with no permanent magnets
available. As such, a greater amount of reluctance torque can be
generated, as compared to the case with no permanent magnets
available.
[0105] Moreover, the permanent magnet 130, by its nature, generates
a magnetic torque through the interaction with the stator 110. That
is, when a pole is formed in the stator 110 by the applied current
to the coil, the pole produced in the stator 110 interacts with the
pole of the permanent magnets 130 because of a relative positional
relationship between the permanent magnets 130 and the rotor 120,
and a magnetic torque is consequently generated.
[0106] As noted earlier, the motor in accordance with the present
invention is designed to have a synchronous rotation, after its
startup, by both reluctance and magnetic torque, so it demonstrates
a very high efficiency performance in normal operation mode. This
means that under the same circumstances such as the same motor size
and the same current intensity, the motor in accordance with the
present invention achieves a very high efficiency performance, as
compared with the conventional induction motor.
[0107] With reference to FIGS. 3 through 5, the following will now
explain in detail about the configuration of a rotor included in
the motor in accordance with the present invention.
[0108] The rotor 120 includes a rotor core 123 as its basic
structural component, and a flux barrier 140 formed at the rotor,
more specifically, at the rotor core 123.
[0109] Then, there is a q-axis formed in a radius direction from
the center of the rotor, along which flux flow being impeded
through the flux barrier 140. And there is a d-axis formed in a
radius direction from the center of rotor, along which flux flow is
not impeded.
[0110] Alternatively, the rotor may include a plurality of flux
barriers arranged in the circumference direction of the rotor to
form an even number (at least two or more) of poles as depicted in
FIG. 3. As an example, if the flux barriers are arranged to form
two poles, the q-axis lies at right angles to the d-axis as in FIG.
3. If the flux barriers are arranged to form four poles, though not
shown, the q-axis lies at 45 degrees to the d-axis.
[0111] Another thing to notice in FIG. 3 is that the flux barriers
140 are preferably formed to be symmetric with respect to the
q-axis. By this configuration, the reluctance torque is made
symmetric with the q-axis and the occurrence of noises or
vibrations due to the deviation of reluctance torque can be
prevented.
[0112] Further, the flux barrier 140 preferably has a structure
having at least two layers. As an example, at least two flux
barrier layers may be formed over the upper and lower faces of the
rotor shown in FIG. 3. This structure enables to increase the
percentage of area occupied by the flux barriers 140 in the rotor
core 123 in the q-axis direction, and therefore raises the
reluctance in the q-axis direction.
[0113] For the same reason, it is more desirable to arrange the
flux barriers 140 more distant from or closer to an axis that is
orthogonal to the q-axis. In other words, instead of forming the
flux barriers 140 parallel to the d-axis as shown in FIG. 3, it is
more preferable to make the flux barriers 140 have a convex upward
configuration or a concave downward configuration with respect to
the d-axis. Such configuration of the flux barriers 140 may be
angulated or may form an arc shape.
[0114] Moreover, as shown in FIG. 3, the flux barriers 140 located
nearer to the center of the rotor, or the flux barriers 140 formed
on an inner side, are longer in order to increase the reluctance in
the q-axis direction even more.
[0115] Meanwhile, the conductor bars 122 positioned within an angle
(.alpha.) between both ends of the outermost flux barrier 140 and
the center of the rotor have a smaller width in the radius
direction than that of other conductive bars. It is so because a
gap between the conductive bar 122 and the flux barrier 140 will
become very narrow if the radial width of the conductive bars 122
provided within the angle (.alpha.) increases. As such, a leakage
flux is highly likely to occur due to flux saturation in the d-axis
direction. That is, in order to stably secure a sufficient gap, the
radial width of the conductive bars 122 provided within the angle
(.alpha.) should be reduced.
[0116] Referring now to FIG. 4 and FIG. 5, an end of the flux
barrier 140 is very close to and faces the slot 121. That is to
say, a gap between the end of the flux barrier 140 and the slot 121
should be minimized in order to prevent the flux having been formed
along the d-axis from leaking through the gap as much as possible.
This is because the flux leakage through the gap eventually reduces
the reluctance difference in the q- and d-axis directions that
much.
[0117] However, there are certain limitations to reduce the gap
between the end tip of the flux barrier 140 and the slot 121, or
the gap between the end tip of the flux barrier 140 and the
conductive bar 122 formed in the slot 121. This is because the gap
portion could be burst out under pressure when the conductive bars
122 are formed in the slots 121 by aluminum die casting, only to
introduce molten aluminum to the flux barriers 140. Therefore, to
get rid of such worries and yet to obtain a sufficiently small gap,
the end tip of the flux barrier 140 should be smaller in width than
other areas. Examples of this are shown in FIGS. 5a through 5c.
Through those examples, one can minimize a distance between the
flux barrier 140 and the slot 121 facing each other and minimize an
area that can possibly burst out under pressure, thereby reducing
the gap that much.
[0118] Meanwhile, the motor in accordance with the present
invention includes permanent magnets 130 provided to produce flux
inside the rotor core and further a magnetic torque. As depicted in
FIG. 3 and FIG. 4, the permanent magnets 130 can be inserted into
some of the flux barriers 140. Needless to say, the permanent
magnets 130 can be inserted into all layers of the flux barrier
140, or the permanent magnets 130 may not be inserted into
particular layers of the flux barrier 140.
[0119] The flux barrier 140 may be formed continuously in a
longitudinal direction. Preferably, two or more permanent magnets
130 should be provided to one flux barrier 140 in a continuous form
along the longitudinal direction. This is done so because it is
very hard to form a single permanent magnet 130 that fits the
configuration of the flux barrier, and because plural permanent
magnets 130 are more advantageous and more effective to minimize
the flux leakage produced by them alone.
[0120] For the same reasons, there are at least two permanent
magnets 130 provided in the longitudinal direction of the rotor
120, namely, in the height direction of the rotor 120.
[0121] Because of these particular requirements, substantially
uniform shaped (e.g., bar-shaped) unit permanent magnets are
eligible for the permanent magnets 130 for the present invention.
Moreover, the use of bar-shaped unit permanent magnets contributes
to a cost reduction in the fabrication of permanent magnets, and
application of a minimal number of parts that leads to an easier
and simplified manufacturing process.
[0122] In addition, the flux barrier 140 has a specific seat
portion to define the location of the permanent magnet 130. In
other words, a stepped portion 141 as illustrated in FIG. 5b and
FIG. 7 is formed at the flux barrier 140 to be used as an insertion
position of the permanent magnet 130. Such a seat portion also
serves to prevent the permanent magnet from moving out of
position.
[0123] With reference to FIGS. 6 through 12, the following will now
explain in detail about a manufacturing method of a motor, a rotor
to be more specific, in accordance with the present invention.
[0124] Referring first to FIG. 6, one embodiment of the motor in
accordance with the present invention includes a rotor core 123
composed of three different types of unit rotor cores 124, 125, and
126. This particular type motor shown in FIG. 6 is suitable for a
drive motor of a work machine.
[0125] The rotor core is prepared by stacking blanked unit rotor
cores, and those unit cores may adopt three different
configurations.
[0126] As noted earlier, the unit core 125 forming the intermediate
parts of the rotor core 123 may include slots 121 for housing
conductive bars, an axial bore 128 to which a shaft is inserted,
and flux berries 140.
[0127] Meanwhile, the unit core 126 forming the lowermost part of
the rotor core 123 may include only an axial bore 128 and slots
121, as depicted in FIG. 6 and FIG. 8. In other words, the unit
core 126 does not have any flux barriers. In this way, although
permanent magnets 130 may be inserted into some of the flux
barriers 140 for the unit cores 124 and 125, the unit core 126
ensures that those insert permanent magnets 130 do not come out of
place.
[0128] Referring to FIG. 6 and FIG. 7, the unit core 124 forming
the uppermost part of the rotor core 123 includes an axial bore
128, slots 121, and flux barriers 140. Preferably, the unit core
124 has a minimal number of flux barriers 140 for the insertion of
permanent magnets, taking a relationship with an end ring
(description will be followed) into consideration.
[0129] Therefore, even after the rotor core 123 is prepared in a
stacked structure as shown in FIG. 6 and an end ring is formed
through aluminum die casting, it is still possible to insert
permanent magnets 130 into the flux barriers 140. Further, if the
motor can be assembled as shown in FIG. 6, the permanent magnets
would not fly off because of the interaction between the inside
rotor core 123 and the permanent magnets 130 without necessarily
using a special mechanism for preventing the fly-off of the
permanent magnets 130.
[0130] FIG. 9 and FIG. 10 respectively show a plan view and a
bottom view of the rotor core discussed so far. In this type of
rotor core 123, at least one annular (ring-shaped) end ring 151 in
a conventional art may be formed underneath the rotor core 123 as
depicted in FIG. 12.
[0131] To be short, the rotor 123 of this embodiment is designed in
a manner to insert permanent magnets 130 after forming the end
ring(s) 151.
[0132] The conventional annular end ring may cover both top and
bottom faces of the rotor core 123, except for the axial bore 128.
In general, an end ring 151 having a greater thickness in the
height direction and the width direction is effective for keeping
the loss through the end ring to a minimum. That is to say, similar
to the loss in conductive bars, the loss produced by the end ring
151 can be minimized.
[0133] However, there is a height limitation in the end ring 151
for fear the motor will get bulky. Therefore, it is safer to make
the end ring 151 thicker in the width direction in order to
minimize the loss produced by the end ring 151.
[0134] Meanwhile, the uppermost unit core 124 shown in FIG. 6 can
be substituted with the lowermost unit core 126 shown in FIG. 8.
That is, the unit core 126 in FIG. 8 can be used for both the
uppermost and lowermost unit cores. In effect, this configuration
is another possible embodiment of the motor in accordance with the
present invention. To make such configuration, a lowermost unit
core 126 and an intermediate unit core 125 are stacked first, and
permanent magnets 130 are then inserted into flux barriers 140.
Next, an uppermost unit core (in this particular case, this is
identical with the lowermost unit core) is stacked. Lastly,
conductive bars and end rings are formed by aluminum die
casting.
[0135] FIG. 10 illustrates the bottom view of the rotor core having
such configuration. Given that the rotor core has the configuration
described above, any conventional annular end rings 151 as shown in
FIG. 9 can be provided to the upper and lower portions of the rotor
core.
[0136] That is, the rotor 120 of this embodiment is designed in a
manner to form the end rings 151 after inserting the permanent
magnets 130. Therefore, although a motor having the rotor 120 of
this embodiment may not be a direct drive type motor, it is still
possible to prevent the fly-off of the permanent magnets 130 with
the help of the uppermost and lowermost unit cores.
[0137] In every configuration of a motor in accordance with the
present invention, the end rings 151 are provided not to impede or
not to interfere with the performance magnets 130, and form a short
circuit with the plural conductive bars 122. Needless to say, the
end rings 151 should be provided in a manner not to interfere with
the flux barriers 140 also.
[0138] That is, in another embodiment of the motor discussed
earlier, no flux barrier 140 is formed on the uppermost and
lowermost parts of the rotor motor 123. In result, the end rings
151 do not interfere with the flux barriers 140. Therefore, end
rings taking on any conventional configuration may be utilized, and
the loss produced by the end rings 151 can be minimized.
[0139] As described above, however, one embodiment of the motor is
designed in a manner to form end rings 150 after a rotor core is
formed. Permanent magnets 130 are then inserted into flux barriers
140. Thus, the end rings 150 should not interfere with the
permanent magnets 130. In other words, the end rings 150 are formed
in such a way that there is a space reserved for the insertion of
the permanent magnets 130.
[0140] In addition, end rings 150 having a larger radial width are
preferred to keep the loss by the end rings 150 to a minimum. In
this case, therefore, the uppermost unit core 124 is provided with
a minimal number of flux barriers 140 for the insertion of
permanent magnets.
[0141] In this case, an end ring 150 having a similar configuration
to the ones in FIGS. 9 and 11 can be formed. Particularly, one can
minimize the loss due to the end ring 150 by increasing the width
in the d-axis direction. Since the width in the q-axis direction
can also be increased, the flux barriers 140 are arranged to
converge towards the center of the rotor as depicted in FIG. 9.
Meanwhile, the end rings 150 arranged in the d-axis direction are
in parallel with the q-axis.
[0142] In addition, end rings formed in the q-axis direction are
preferably in parallel with adjacent flux barriers.
[0143] Thus, end rings 150 of this embodiment form an annular shape
featuring variable radial widths along the circumferential
direction of the rotor core 123. Also, the width in the q-axis
direction is greater than the width in the d-axis direction.
[0144] With reference to FIGS. 13 through 15, the following will
now explain in detail about the operation of a motor in accordance
with the present invention.
[0145] Basically, the motor in accordance with the present
invention can be applied to variable-load fan motors, compressors,
home appliances, and so forth. In the interest of brevity and
convenience, however, the description hereinafter will focus on the
application of the motor in a rotary compressor.
[0146] In general, a single phase induction motor is often used for
rotary compressors. Due to nature of the single phase induction
motor as noted earlier, such a rotary compressor has the
disadvantage of a low efficiency. In light of this, the motor in
accordance with the present invention can be advantageously used to
achieve a very high efficiency of rotary compressors or the
like.
[0147] Meanwhile, a capacity modulation rotary compressor which
operates at a variable capacity has recently been used widely.
[0148] As an example, there are compressors with a variable
capacity depending on the amount of compressed refrigerant in one
cylinder. Also, there are other compressors with a variable
capacity by selectively compressing refrigerant in plural
cylinders, as disclosed in Korean Patent Application Publication
No. 10-2006-0120387.
[0149] In the latter case, the compressor is provided with plural
cylinders, and compression of refrigerant occurs in the cylinders.
Driven by one motor, refrigerants are compressed in some cylinders,
while refrigerants in other cylinders are selectively compressed
depending on load on the compressor.
[0150] Having a variable capacity for the compressor indicates a
change in motor load for refrigerant compression. Therefore, by the
use of the motor in accordance with the present invention, not the
conventional induction motor, a capacity modulation compressor can
demonstrate a very high-efficiency performance.
[0151] This is possible because the motor in accordance with the
present invention always runs at a synchronous speed in normal
operation as well as under variable load, thereby making
substantial improvements in the motor efficiency in normal
operation. Besides, even if the temperature of the motor may
increase, since the motor runs by a reluctance torque and a
magnetic torque, loss in relation to the temperature rise can be
minimized.
[0152] FIG. 13 is a graph illustrating the relationship between
starting torque and capacitor.
[0153] As can be seen from the graph, starting torque increases in
proportion to capacitor. To make a motor start, the starting torque
should have a certain value or higher. That is to say, the starting
torque should be high enough to overcome an initial load of the
motor. In other words, if the motor has a high initial load, the
magnitude of a starting torque for a startup of the motor has to be
even greater than that.
[0154] Meanwhile, a coil circuit including only one capacitor is
shown in FIG. 3. In this case, the capacitor should have a value
which is high enough to meet a variance in load on the motor and to
start the motor under such a variable load. However, if a
large-value capacitor is used despite a small load on the motor,
loss occurs in the motor to that extent. Therefore, the capacitor
value should vary in accordance with a variance in the motor
load.
[0155] In detail, a coil includes a main wiring connected to a
single phase power supply and an auxiliary wiring connected to the
single phase power supply, in parallel to the main wiring. And two
parallel capacitors are connected serially to the auxiliary wiring.
In other words, a circuit in FIG. 15 is configured to substitute
the capacitor in FIG. 3.
[0156] Here, when a switch 3 is turned on, a sum of the two
capacitor values connected in parallel to each other represents the
value of a capacitor. Thus, when the switch 3 is on, a large
capacitor value is obtained, and a starting torque increases even
more. On the contrary, when the switch 3 is off, only one capacitor
value is produced, and a starting torque is relatively small.
[0157] Meanwhile, during an initial startup of a motor, in other
words, during an initial startup of a compressor, one can preset
the capacity for the compressor. That is, the compressor can be
preset to run in high capacity or in low capacity.
[0158] Moreover, it is preferably to make the motor start quickly
and enter the normal operation mode. Therefore, in order to make
the initial startup quicker and obtain a good, stable startup, the
switch should always be in the "ON" position during the initial
startup of the motor. That is to say, the switch should remain
activated all the time in the startup operation, independent of a
preset capacity.
[0159] FIG. 14 illustrates one example of a capacitor included in a
motor in accordance with one embodiment of the present invention,
FIG. 15 briefly illustrates a circuit diagram of a stator coil and
a capacitor included in a motor in accordance with the present
invention, FIG. 16 graphically illustrates how a current flow in a
startup capacitor of the present invention changes with respect to
time, and FIG. 17 is a graph comparing torque a motor in accordance
with the present invention produces with torque a motor driven by a
conventional capacitor produces. During the startup phase, an LSPRM
motor like the motor in accordance with the present invention
produces a braking torque by permanent magnets in the opposite
direction of an induction torque. As a result, the induction torque
may become less than a real load torque such that the startup
performance is impaired, as compared with a conventional single
phase induction motor. To resolve this, during the startup phase,
the capacity of a capacitor being serially connected to a stator
coil should be increased. However, once a motor enters the normal
operation mode after the startup phase, the motor runs at a preset
synchronous speed and thus, load on the motor is lessened.
Therefore, if a capacitor with high capacity is used even in the
normal operation mode, a power loss occurs naturally. One
preferable way to avoid such a problem is using a high-capacity
capacitor for the startup operation of a motor, while using a
low-capacity capacitor for the normal operation.
[0160] Referring to FIG. 14, an integrated capacitor unit 115 for
the motor of the present invention includes a capacitor CR for use
in the normal operation mode (`normal operation capacitor`) and a
capacitor CS for use in the startup mode (`startup capacitor),
which are installed in a casing 210. A terminal 220 of the normal
operation capacitor CR, a terminal 230 of the startup capacitor CS,
and a power supply terminal 240 are positioned at one side of the
casing 210. A discharge resistor 232 is attached to the terminal
230 of the startup capacitor CS and dissipates electricity having
been stored in the startup capacitor CS when the capacitor CS is
not in use.
[0161] Referring to FIG. 15, an electrical switch is serially
connected to the startup capacitor CS. When the motor gets out of
the startup phase and enters the normal operation phase where the
motor runs synchronously by a magnetic torque that is produced due
to the permanent magnetic and a reluctance torque that is produced
due to the presence of flux barriers, the electrical switch cuts
off the current flow to the startup capacitor CS. Although the
electrical switch may be turned on/off by a controller (not shown)
that is in charge of the control over the operation of the motor, a
PTC (Positive Temperature Coefficient) device is another convenient
option because it can actively cut off the current flow to the
startup capacitor CS without having to receive a command from the
controller (not shown).
[0162] FIG. 16 graphically shows how a current flow in the startup
capacitor CS changes with respect to time, given that the startup
capacitor CS has been serially connected to the PCT device. As can
be seen from the graph, after a certain period of time the current
flow in startup capacitor CS converges almost to zero. That is, no
current flow to the startup capacitor CS after a certain period of
time, and current flows only to the normal operation capacitor CR
such that the total capacity of capacitors becomes lower. As such,
one can control the capacity of capacitor(s) suitably for the line
start permanent magnet reluctance motor to which a smaller load is
applied during the normal operation mode than in the startup
mode.
[0163] Referring to FIG. 17, the sum of the capacity of the normal
operation capacitor CR and the capacity of the startup capacitor CS
should be sufficiently large for the induction torque of the motor
to be greater than at least load torque. The motor torque during
startup increases in proportion to the capacity of capacitor(s).
According to the graph in FIG. 17, instead of the both the normal
operation capacitor CR and the startup capacitor CS together, if
the normal operation capacitor CR is used alone to start a motor,
the motor can only generate a smaller induction torque than the
load. This is why in the present invention motor the startup
capacitor CS is connected in parallel with the normal operation
capacitor CR. In so doing, the capacity of capacitors increases and
a greater starting torque is induced. When the speed of motor reach
the synchronous speed, the motor is driven by a magnetic torque
produced due to the permanent magnetic and by a reluctance torque
produced due to the presence of flux barriers. As shown in FIG. 17,
the maximum torque produced by the motor in accordance with the
present invention is equivalent to the maximum torque produced by
any of conventional induction motors.
[0164] FIG. 18 illustrates a compressor in accordance with a first
embodiment of the present invention. In particular, a capacity
modulation rotary compressor is illustrated as an example, which
the compressor includes a casing 100 defining hermetic space S; a
motor used as a driving unit that is fixed inside the casing 100
and includes a stator and a rotor (to be described); a plurality of
compressor units, including a first compressor unit 30, a second
compressor unit and a third compressor unit 50, installed inside
the casing 100 and connected to the motor to compress a
refrigerant; an accumulator A where a working fluid having passed
through an evaporator of the refrigeration cycle is separated into
liquid and vapor components; suction pipes 30s, 40s, and 50s, via
which the working fluid is sucked into the compressor units 30, 40,
and 50, respectively, from the accumulator A; and suction valves
40v and 50v mounted on the suction pipes 40s and 50s, for
opening/closing the suction pipes 40s and 50s so as to regulate the
suction flow of the working fluid into the compressor units 40 and
50. The motor includes a stator 10 fixed inside the casing 100, for
receiving electric power from outside; a rotor 120 arranged inside
the stator with a predetermined gap there between to rotate
engagedly with the stator 110; and a shaft 23 integrally formed
with the rotor 120, for transferring a drive force to the
compressor units 30, 40 and 50.
[0165] To see how the capacity modulation compressor works, when
power is applied to the stator 110 included in the motor and the
rotor 120 starts rotating, the shaft 23 also rotates engagedly with
the rotor 120 and transfers the torque of the motor to the first
through third compressor units 30, 40 and 50, such that the
compressor produces either a large cooling capacity while operating
in a high power mode, or a small cooling capacity while operating
in a power saving mode, under proper regulations of the suction
valves 40v and 50v complying with a required capacity by an air
conditioning system.
[0166] The following will now explain the operating method of a
capacity modulation compressor in accordance with one embodiment of
the present invention. The capacity modulation compressor of the
present invention includes a plurality of compressor units 30, 40
and 50, and a motor functioning as an electromotive driving unit
for driving the compressor units 30, 40 and 50. As noted earlier, a
line start permanent magnet reluctance motor is utilized as the
electromotive driving unit 20. In other words, during the startup
of such a capacity modulation compressor, the motor starts running
by an induction torque that is produced by conductive bars 122 of
the rotor 120, but, in the normal operation, it is driven by a
reluctance torque produced due to the presence of flux barriers 140
and a magnetic torque produced due to the permanent magnets 130 and
operates at a synchronous speed in synchronous with a given power
frequency. Thus, it becomes possible to lower power loss occurring
in the conductive bars 122 of the rotor 120. Meanwhile, during the
startup operation, the magnetic torque that is produced due to the
presence of the permanent magnets 130 works in the opposite
direction to the induction torque that is produced due to the
presence of the conductive bars 122, functioning as a braking
torque or a load.
[0167] Unlike a single phase induction motor which is a type of
asynchronous motor, the line start permanent magnet reluctance
motor is a type of synchronous motor, so an induction torque equal
to or only slightly higher than a load torque is sufficient to
cause the motor to run at a speed close to the preset synchronous
speed. Even if the controller (not shown) might have started the
capacity modulation compressor in accordance with the present
invention under low load and thus only a relatively low induction
torque was produced in the conductive bars 122 of the rotor 120,
the capacity modulation compressor of the present invention can
still demonstrate an enhanced power efficiency because an induction
torque not lower than a load torque is already secured.
[0168] Here, the controller (not shown) makes the capacity
modulation compressor start to rotate under conditions of lower
load than the maximum load condition. In the case of the capacity
modulation compressor in accordance with one embodiment of the
present invention as depicted in FIG. 18, if the compressor is
started, under the control of the controller (not shown) with all
of the suction valves 40v and 50v being closed, a working fluid is
compressed only in the first compressor unit 30 so that a minimum
load is applied to the motor. On the other hand, if the capacity
modulation compressor is started with only one of the suction
valves 40v and 50v being closed, a working fluid is compressed in
the first compressor unit 30 and in one of the second and third
compressor units 40 and 50, so a load still lower than a maximum
load is applied to the motor.
[0169] Although the first, second and third compressor units 30, 40
and 50 may have the same amount of compressing capacity, i.e.,
placing the same load on the electromotive driving unit 20, if they
have different capacities, the compressed capacities of the
compressor units 30, 40 and 50 can be in more diverse combinations.
Therefore, it is better to let them have different capacities.
[0170] FIG. 19 illustrates a compressor in accordance with a second
embodiment of the present invention. The compressor of this
embodiment includes: a casing 100 where plural gas suction pipes
SP1 and SP2 and a gas discharge pipe DP are housed, communicating
with each other; a motor 20 installed at the upper side of the
casing 100, for generating a torque; a first and a second
compressor unit 30 and 40 installed at the lower side of the casing
100, for compressing a refrigerant with the motor-generated torque;
and a vane control unit 50 connected to the intermediate section
between the plural suction pipes SP1 and SP2 and the discharge pipe
DP, for switching a rear face of a second vane 44 (to be described)
from high pressure atmosphere to low pressure atmosphere, for
supporting the second vane 44 as well as supplying a high pressure
to a lateral face of the second vane, so as to selectively control
the second vane 44 based on a difference between the pressure
applied to the rear face of the second vane 44 and the pressure
applied to the lateral face of the second vane 44.
[0171] The motor 20 includes a stator 21 and a rotor 22, and its
detailed structure can be referred back to the discussions in
conjunction with FIG. 3 through FIG. 17.
[0172] The first compressor unit 30 is constituted by a first
annular cylinder 31 installed inside the casing 10; an upper
bearing plate (hereinafter, an upper bearing) 32 and an
intermediate bearing plate (hereinafter, an intermediate bearing)
33 for covering both upper and lower side of the first cylinder 31
to form a first compression space V1 together and for supporting
the shaft 23 in a radius direction; a first rolling piston 34
rotatably connected to an upper side eccentric portion of the shaft
23, for compressing a refrigerant while rolling in the first
compression space V1 of the first cylinder 31; a first vane 35
movably connected to the first cylinder 31 in a radius direction to
be contacted with an outer peripheral surface of the first rolling
piston 34, for partitioning off the first compression space V1 of
the first cylinder 31 into a first suction chamber and a first
compression chamber; a first vane spring 36 taking the form of a
compression spring to resiliently support the rear side of the
first vane 35; a first discharge valve 37 openably connected to an
end of a first discharge port 32a, for regulating discharge of
refrigerant vapor coming out of the first compression chamber in
the first compression space V1; and a first muffler 38 provided
with a predetermined interior spatial volume to receive the first
discharge valve 37 and connected to the upper bearing 32.
[0173] The second compressor unit 40 is constituted by a second
annular cylinder 41 installed underneath the first cylinder 31
housed in the casing 10; an intermediate bearing 33 and a lower
bearing 42 for covering both upper and lower side of the second
cylinder 41 to form a second compression space V2 together and for
supporting the shaft 23 in both radial and axial directions; a
second rolling piston 43 rotatably connected to a lower side
eccentric portion of the shaft 23, for compressing a refrigerant
while rolling in the second compression space V2 of the second
cylinder 31; a second vane 44 movably connected to the second
cylinder 41 in a radius direction to be contacted with or separated
from an outer peripheral surface of the second rolling piston 43,
for partitioning off the second compression space V2 of the second
cylinder 41 into a second suction chamber and a second compression
chamber both being able to communicate with each other; a second
discharge valve 45 openably connected to an end of a second
discharge port 42a that is formed near the center of the lower
bearing 42, for regulating discharge of refrigerant vapor coming
out of the second compression chamber; and a second muffler 46
provided with a predetermined interior spatial volume to receive
the second discharge valve 45 and connected to the lower bearing
42.
[0174] The second cylinder 41 includes a second vane slit 41a which
is formed at a portion on the inner peripheral surface defining the
second compression space V2, for allowing the second vane 44 to
reciprocate in a radius direction along with it; a second suction
port 41b extending in a radiation direction, which is formed at one
side of the second vane slit 41a, for guiding a refrigerant to the
second compression space V2; and a second discharge guide groove
41c extending in an axial direction at a tilt angle, which is
formed at the other side of the second vane slit 41a in an axial
direction, for discharging a refrigerant into the casing 10.
Moreover, a back pressure space 41d having a predetermined interior
spatial volume is formed on the rear radial side of the second vane
slit 41a, so as to create a suction- or discharge-pressure
atmosphere behind the second vane 44 through the communication with
a back pressure connection pipe 53 of the vain control unit 50.
Further, a lateral pressure passage 41e is formed in a direction
orthogonal to the movement direction of the second vane 44, or at a
predetermined stagger angle, so as to control the second vane 44
with a discharge pressure by letting the second vane slit 41a
communicate with the interior of the casing 10.
[0175] The back pressure space 41d is given a predetermined
interior spatial volume that, although the second vane 44 may have
fully retreated and inserted into the second vane slit 41a via the
common connection pipe 53 (to be detailed) of the vane control unit
50, the rear face of the second vane 44 forms a pressure side for
an input pressure that is transferred via the common connection
pipe 53.
[0176] The lateral pressure passage 41e is formed on the discharge
guide groove 41c side of the second cylinder 41 with respect to the
second vane 44. Preferably, a plurality of lateral pressure
passages (on both upper and lower ends as shown in the drawing) are
formed in the height direction of the second vane 44. In addition,
the total cross-section area of the lateral pressure passage 41e
should be equal to or smaller than area of a pressure side applying
pressure to the rear face of the second vane 44 through the back
pressure space 41d, such that the second vane 44 may not be
controlled extremely. If necessary, the second cylinder 41 can be
designed to occupy the same volume with or a different volume from
the first cylinder 31 in the first compression space V1. In the
former case where the two cylinders 31 and 41 have the same volume
with each other, the compressor capacity can be cut down to half
(50%) because only one of the cylinders will work if the other
cylinder works in power saving mode. In the latter case where the
two cylinders 31 and 41 have different volumes, the compressor
capacity varies as much as volume ratio of the other cylinder in
normal operation mode.
[0177] The vane control unit 50 comprises a low pressure side
connection pipe 51 communicating with the suction side of the
second cylinder 41; a high pressure side connection pipe 52
communicating with the discharge side of the second cylinder, or
with the interior space of the casing 10 to be more accurate; a
common connection pipe 53 connected alternately to both the low
pressure side connection pipe 51 and the high pressure side
connection pipe 52, so as to communicate with the back pressure
space 41d of the second cylinder 41; a three-way valve 54
functioning as a back pressure switch valve, which is installed at
a junction of the low pressure side connection pipe 51, the high
pressure side connection pipe 52, and the common connection pipe 53
to alternately connect the common connection pipe 53 to the other
two connection pipes 51 and 52; and a lateral pressure supply unit
provided to the second cylinder 41, for supplying a discharge
pressure to the lateral face of the second vane 44 so that the
second vane 44 is closely adhered to the second vane slit 41a of
the second cylinder 41.
[0178] The low pressure side connection pipe 51 is connected
between the suction side of the second cylinder 41 and a gas
suction pipe on the inlet side of the accumulator 5/a gas suction
pipe (the second gas suction pipe) SP2 on the outlet side of the
accumulator 5.
[0179] The high pressure side connection pipe 52 may be designed to
communicate with the lower part of the casing 10, such that oil
(fluid) is introduced directly into the back pressure space 41d
from the casing 10, but it may also be branched in the center of
the gas discharge pipe DP. As the back pressure space 41d is sealed
in this case, oil might not be supplied between the second vane 44
and the second vane 44 and the second vane slit 41a, so frictional
loss is likely to occur. To overcome the frictional loss,
therefore, an oil feed hole (not shown) may be formed at the lower
bearing 42 to enable oil to be fed when the second vane 44
reciprocates.
[0180] As described above, for the lateral pressure supply unit,
there is at least one lateral pressure passage 41e (e.g., two
passages in the both upper and lower sides as in the drawing)
formed in the second cylinder 41, so as to facilitate the transfer
of discharge pressure from casing 10 in the thickness direction of
the second vane 22. However, it is more desirable to form the
lateral pressure passages in the discharge guide groove 41c side
with respect to the second vane 44 and to make all of the passages
have a uniform cross-section area in the height direction of the
vane.
[0181] Although a capacity modulation compressor has mainly been
explained as an example of rotary compressor, one should notice
that sealed type compressors or scroll compressors can also employ
a line start permanent magnet reluctance motor as their power
transmission unit.
[0182] The following will now explain about a startup operation for
the compressor in accordance with the first or second embodiment of
the present invention as illustrated in FIG. 18 or FIG. 19. FIG. 20
is a graph comparing a starting torque produced by a motor included
in a compression mechanism in accordance with the present invention
with a starting torque produced by a conventional induction
motor.
[0183] As evident in the graph of FIG. 20, the starting torque of
an electromotive driving unit is considerably less than the
starting torque of a conventional induction motor. However, when a
line start permanent magnet reluctance motor is concerned, it is
only required to generate an induction torque greater than a load
torque, assuming that the motor is operating at a preset
synchronous speed or lower. Here, load being applied to the
electromotive driving unit when the compressor unit of a capacity
modulation compressor compresses a working fluid varies depending
on compressing capacity of the compressor unit of interest. That
is, if a compressor unit compresses a working fluid (e.g.,
refrigerant, refrigerant oil, etc) with a lower capacity, a smaller
load is placed on the electromotive driving unit. As in the graph,
a load (Load 1) assigned to the electromotive driving unit when a
compressor unit having the maximum capacity (100%) compresses a
working fluid is smaller than a load (Load 2) assigned when a
compressor unit having a capacity less than the maximum value
(<100%) compresses a working fluid (<100%). Also as mentioned
above, a large starting torque of an electromotive driving unit
included in the capacity modulation compressor of the present
invention is not always desirable, because the starting torque of
the electromotive driving unit is only required to have a slightly
higher value than the load torque. Therefore, power efficiency of a
compressor can be improved markedly by keeping the load torque to a
minimum and by maintaining the starting torque at a value only
slightly higher than the minimum load torque.
[0184] Under such configuration, the compression mechanism of the
present invention can be driven in power saving mode where only
some of the compressor units 30, 40 and 50 (refer to FIGS. 18 and
19) for the compression mechanism are involved in the compression
of a working fluid required for a startup. As a result, a smaller
load is put on the motor of the compressor, so that the startup
operation can easily be performed even by a relatively low starting
torque.
[0185] As the load assigned to the electromotive driving unit can
be reduced by regulating the compressing capacity of a compressor
unit, one can improve startup properties of a compressor driven by
a line start permanent magnet reluctance motor that functions as
the electromotive driving unit running not only on single-phase
power, but also on two-phase or three-phase power.
[0186] FIG. 21 illustrates an air conditioning system in accordance
with one embodiment of the present invention. In particular, the
air conditioning system of the present invention can be
advantageously used in a broad space or in areas either too cold or
too hot where speedy operations to provide a pleasant indoor
climate within a proper temperature range is very much appreciated,
by connecting a plurality of indoor units 201, 202, and 203 to one
outdoor unit 1000 including compressors 101 and 102 and a condenser
300. For the air conditioning system to operate in combined cooling
and heating mode, the outdoor unit 1000 should be equipped with a
four-way valve 400 for controlling the direction of fluid flow.
[0187] The plurality of indoor units 200 are selectively operated
in response to user manipulation. In this manner, capacity of the
compressors that is actually required of the indoor unit 200 varies
depending on each case. If the outdoor unit 1000 is provided with
only one constant speed compressor designed to have a maximum
capacity, a waste of energy will always remain as a problem because
the compressor has excess capacity in case the indoor unit 200 is
driven at lower capacity than a maximum. Meanwhile, if the outdoor
unit 100 is equipped with a capacity modulation compressor driven
by an inverter motor, one can modulate the compressing capacity to
comply with cooling capacity requirement of the indoor unit 200,
but the use of such an expensive component like the inverter driver
only lowers price competitiveness. Besides, because the driver
itself consumes electricity, power efficiency of the system will
also suffer a loss to a certain degree.
[0188] To resolve these problems, the air conditioning system in
accordance with the present invention is provided with an indoor
unit 200 including plural compressors connected to each other
serially and/or in parallel. At least one of the plural compressors
is a capacity modulation compressor similar to the one described
with reference to FIG. 18 or FIG. 19, and a line start permanent
magnet reluctance motor is employed as an electromotive driving
unit for the capacity modulation compressor.
[0189] Thus, one embodiment of the air conditioning system of the
present invention includes plural indoor units 200 accommodated in
a broad space together or in a plurality of defined spaces
separately. By selectively operating the indoor units 201, 202,
203, cooling and heating operations can be done only in
predetermined or selected spaces.
[0190] The indoor units 201, 202, and 203 are connected to each
other in parallel, and there is a controller (not shown) for
controlling each of the indoor units and the outdoor unit 1000. A
user can select indoor unit(s) to be operated and a load (cooling
capacity) of the selected indoor unit(s) 201, 202, and 203. In
response to user inputs regarding the indoor unit(s) to be operated
and the load (cooling capacity) of the selected indoor unit(s) 201,
202, and 203, the controller (not shown) controls the compressing
capacity of the compression mechanism included in the outdoor unit
1000.
[0191] For example, suppose that the outdoor unit 1000 is provided
with two compressors 101 and 102. Examples of possible
configuration that can come out of this condition are using two
capacity modulation compressors, using one capacity modulation
compressor and one fixed-capacity compressor in combination, and
using one capacity modulation compressor and one inverter
compressor in combination. Likewise, suppose that the outdoor unit
1000 is provided with three compressors. In this case, two fixed
capacity compressors and one capacity modulation compressor can be
used in combination, or one capacity modulation compressor and two
fixed-capacity compressors can be used in combination.
[0192] In the case of using one capacity modulation compressor and
one fixed-capacity, fixed-speed compressor, the fixed-capacity
compressor may have a refrigerant compressing capacity greater or
less than the maximum capacity of the capacity modulation
compressor.
[0193] FIG. 22 is a graph illustrating compressive load on an
outdoor unit including two fixed-capacity, fixed-speed compressors
in a prior art, FIG. 23 is a graph illustrating compressive load of
an outdoor unit including one capacity modulation compressor in
accordance with one embodiment of the present invention and one
fixed-capacity, fixed-speed compressor, FIG. 24 is a graph
illustrating compressive load of an outdoor unit including two
capacity modulation compressors in accordance with one embodiment
of the present invention, and FIG. 25 is a graph illustrating the
load on outdoor unit including one capacity modulation compressor
in accordance with one embodiment of the present invention and one
inverter compressor.
[0194] Referring to the graph in FIG. 22, the compressive load on
the outdoor unit provided with two conventional fixed capacity and
speed compressors can be modulated only in three steps. For
example, suppose that two fixed capacity and speed compressors of
different capacities are used for an outdoor unit. Then, the
compressive load on the outdoor can be adjusted only in three
steps: (i) compressing capacity modulation for a low-capacity
compressor; (ii) compressing capacity modulation for a
high-capacity compressor; and (iii) compressing capacity modulation
for the both low- and high-capacity compressors. Considering that
an outdoor unit may be provided with a larger number of indoor
units, the above-described scheme may not be much efficient to
comply with diverse changes in cooling capacity that are to be
modulated through more than three steps.
[0195] On the contrary, graphs in FIGS. 22 through 25 illustrate
that the compressive load on the outdoor unit of the present
invention can be modulated in multiple steps. This suggests that
the compressive load on an outdoor unit used for a multi-air
conditioning system provided with plural indoor units connected to
the outdoor unit can be adjusted in response to a change in the
required load of the indoor units through several steps.
[0196] While the present invention has been described with respect
to the specific embodiments, it will be apparent to those skilled
in the art that various changes and modifications may be made
without departing from the spirit and scope of the invention as
defined in the following claims.
* * * * *